View full sizeAP Photo/The Seattle TimesIn a Nov. 6 photo, Andrew Johnson, center, with King County Explorer Search and Rescue, talks to a group looking for a missing 2-year-old boy in Bellevue, Wash. Sky Metalwala, 2, has been missing since that day, when he disappeared after his mother says she left him alone in an unlocked car after it ran out of gas. She says she took her 4-year-old daughter with her and when she came back about an hour later, the boy was gone.

SEATTLE -- Facing a dearth of leads in the disappearance of Washington state toddler, investigators expanded their search efforts to a popular suburban park Saturday, combing through fields and brush as the boy’s mother continued to refuse to speak with police.

Volunteers from many organizations -- including professional trackers, searchers on horseback and the King County dive team -- arrived early at Marymoor Park in Redmond. The 640-acre expanse on Lake Sammamish is one of the region's most popular parks, and as teams fanned out in hopes of finding 2-year-old Sky Metalwala, people went jogging, walked their dogs and played soccer games nearby.

Authorities had received no information leading them to the park, but were searching there merely because of its proximity to the apartment complex where the boy lived with his 4-year-old sister and their mother, Julia Biryukova, Bellevue Police Maj. Mike Johnson told a news conference.

Investigators also were taking another look Saturday at the area in Bellevue where Biryukova reported Sky missing last Sunday, claiming he vanished when she left him sleeping alone in her stalled, unlocked car for an hour while she walked to get gas.

Investigators remained frustrated that Biryukova, who was in a nasty divorce and custody fight with Sky's father, refused to meet with them. They had previously asked her to take a lie-detector test, but her lawyer said she was in no emotional condition to do so, and she has not responded to their invitation to speak with them voluntarily, Johnson said.

Biryukova, 30, did speak with police the day she reported the disappearance, accompanying investigators as they drove the route she said she walked from her stalled car to a gas station. But she remains a focus of the investigation because, police say, her story didn't add up. There turned out to be plenty of gas in the car, which was suffering from no apparent mechanical problems when detectives gave it a test-drive.